Intel® Hyperflex™ Architecture High-Performance Design Handbook

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ID 683353
Date 10/04/2021
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5.2.7. Complex Critical Chains

Complex critical chains consist of several segments connected with multiple join points. A join point is indicated with a positive integer in the Register ID column in the Fitter reports. Join points are listed at the ends of segments in a critical chain, and they indicate where segments diverge or converge. Join points indicate connectivity between chain segments when the chain is listed in a line-oriented text-based report. Join points correspond to elements in your circuit, and show how they are connected to other elements to form a critical chain.

The following example shows how join points correspond to circuit connectivity, using the sample critical chain in the following table.

Table 13.  Sample Critical Chain
Path Info Register Register ID Element
REG #1 a
b
REG #2 c
------------ ------------ ------------ ------------
REG #3 d
e
REG #2 c
------------ ------------ ------------ ------------
REG #3 d
f
REG #4 g
------------ ------------ ------------ ------------
g
h
a
Figure 120. Visual Representation of Sample Critical ChainEach circle in the diagram contains the element name and the join point number from the critical chain table.

For long critical chains, identify smaller parts of the critical chain for optimization. Recompile the design and analyze the changes in the critical chain. Refer to Optimizing Loops for other approaches to focus your optimization effort on part of a critical chain.

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